Fluid-translating device



Jan. 192

7 H. F. SCHMWDT FLUID TRANSLATING DEVICE ,-1914 2 Sheets-Slaw? 1 Filed Sept. 14

//\l VENTOR.

HIS ATTORNEY IN FACT Jan. 18, 1927.

H. F. SCHMIDT FLUID TRANSLATING DEVICE 13 4 P. Sheets-Sheet 2 7 Filed Sept. 14

IN VENTOR.

H/S ATTORNEY IN FACT- r l I Ill/l I .An object of the Patented Jan. 18, 1927.

a UNITED STATES PATENT oFncE.

HENRY I. SCHMIDT, OF PITTSB URGH, PENNSYLVANIA, ASSIGNOR 'I'O.WESTINGHOUSi ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA. V

rnurn-rnansnn'rma nnvrcn.

Application filed September 14, 1914. Serial No. 861,629.

This invention relates to fluid translating devices and particularly to devices for maintaining a high vacuum in condensers or similar apparatus,

invention is to produce a fluid translating device ofthe kinetic type in which means are employed for maintainn 1 in which A equals the cross sectional area of itng the'operation of the device substantially constant for practically all varying condi- 10 tions.

l6 lowerto a region of higher pressure, which A further object is to produce a fluid translating device employing the klnetic or velocity energy of the motive fluid delivered to it in transferring fluid from a region of automatically 'iadjusts itself to variations in the quantity of fluid'conveyed, thus preventing fluctuations of pressure in either the region of lower or higher pressure.

I) These and other objects, which will be made apparentto those skilled the art throughout the description of theinventlon,

are attained by apparatus embodying the features herein described and illustrated in the drawings accompanying and forming a part of this applicationf" I In the drawings: I Fig. 1 is a more or less diagrammatic sectional view of a fluid translating device or ejector embodying my invention:

. Fig. 2 is a sectional view which embodies a modification-of my invention.

Fig. 3 is a diagrammatic sectional view of a relay mechanism which may be employed in carrying outmy invention.

Fig. 4 is a diagrammatic sectional view of a dash pot which may be employed .in

connection with the apparatus illustrated in' Fig. 1. I v

Fig. 5 is a diagrammatic sectional view of a relay mechanism which may beemployed in connection with the apparatus illustrated in Fig. 2.

Fig. 6 is a diagrammatic sectional view of a dash pot which may be employed in connection with the apparatus illustrated in Fig. 2. a

In fluid translating devices such,rfor example, as ejectors, which employ a stream or jet of fluid as the propelling medium for exhausting .fluidsfrom a receptacle, or for transferring-fluid from a region of lower to a region of higher pressure, it is necessary to vent upsetting when the ejector is operatin construct the fluid conducting passage i through which the propellingmedium an the medium entrained movein accordance with the following equation,

the tube at any point; V the velocity of the W a constant which is equal to the weight of the media passing the point, in a unit of time.

It will be apparent, therefore, that ifthe fluid translating device or -ejector is designed to attain a high degree of compression under. one set of operating conditions, it will not be suitable for starting or for operating under varying conditions. In order, therefore, to render-.the ejector effective for all varying conditions, it s necessary to vary the dimensions of the fluid conducting or delivering passage in accordancewith variations in the conditions, or to eifect a change, which is the equivalent of changing the dimensions of the passage to meet the varying condition.

In the present application I have illustrated ejectors in which means are employed for varying the effectivearea of the throat of the fluid delivering passage or diffuser in response to variations in the volume of fluid passing fromtheregion of lower pressure through the diffuser to the outlet, or to the regionof higher pressure. It is well known that the pressures existing throughout the diffuser vary in response to variations inthe amount of fluid traversing the diffuser, and it is also well known that in order to pmunder light load,"or at less than its designe capacity, it is'necessary that the pressure,

- at each point along the diffuser, remain substantially constant. I therefore provide means which corresponds in its operation to variations in diffuser pressure and which operates to var the effective throat or the efl'ective area 0 the difiuserf J Referring toFigure 1, the apparatus there illustrated ,as an embodiment of my 1nven-- tion includes a diffuser 3, which is provided with a divergent wall and which communie cates witha chamber 4 having an inlet port or passage 5. The passage 5 is adapted to communicate with a condenser or a receptacle from which fluid or medium is to be withdraw'li. The chamber 4 is also provided with one or more fluid delivery nozzles 6 of any suitable design, but preferably converging-diverging nozzles which are adapted to receive hi h pressure fluid, for example, steam, and after expanding it to the pressure existing in the chamber 4, to discharge it through the diffuser 3. The nozzles, if more than one is employed, are so arranged that in discharging through the chamber 4 and into the diffuser 3, they entrain the fluid or medium in the chamber 4 and with it form a single stream which enters the throat of the diffuser and traverses the diffuser.

Since, in order to provide an eflective ejector, it is necessary that the product of the area of-the conducting passage and the velocity of the medium divided by the specific volume of the medium shall equal a constant which is the weight of medium passing through the ejector in a unit of time; since it also is desirable'to maintain a constant pressure in the chamber 4, the specific volume of the medium will therefore be maintained constant; and since the nozzle or nozzles 6 discharge from a constant initiaLto a constant final pressure, i. e., the pressure in the chamber 4, it is evident that, in order to maintain a condition of stable equilibrium in the diffuser, the area of the difluser must be varied in direct proportion to the variations in the weight of the medium passing through it.

If the area of the throat of the diffuser is not varied, as above set forth, it is evident that, since the weight of the medium is varying while specific volume of the medium in the chamber 4 remains constant, the velocity of the medium passing, through the throat must vary, that is, decrease if the weight of medium passing decreases, and increase if the weight of medium passing increases, In

order to compress or discharge medium from the chamber 4 through the outlet of the diffuser 3, a definite amount of work per unit weight of medium must be performed, and this work of compression ortranslation must be provided by the kinetic energy of the medium at the entrance of the diffuser. Consequently if the velocity of the medium at the entrance decreases so that the kinetic energy of the medium is less than the work necessary to move the medium from the lower to the higher pressure, it is apparent that the medium will not be discharged from the outlet of the diffuser. Under such conditions the velocity of the medium in the diffuser drop to zero, and not only no work of compression will be accomplished, but fluid will flow from the region of higher pressure or 5 the outlet end of the diffuser into the region will immediately of the parts and to insure the proper operaof lower pressure, or the chamber 4. This result is technically known as upsetting, to

through the throat so as to maintain a condition of equilibrium for all rates of fluid or medium delivery.

The piston 8 is mounted in a cylinder 9, to one end of which, as for example above the piston, the pressure existing in the chamber 4 is transmitted through a pipe or passage 10, and to the other end 'of which, or below the,piston, the pressure existing at some point along the diffuser, is transmitted through a pipe or passage 11. I also provide some means, such for example, as a light coiled spring 12, for yieldingly' resisting movement-of the piston in response to a preponderance of pressure introduced through the pipe 11.

' The spring serves the purpose of insuring a definite position of the piston 8, and consequently of the plug 7, for each increment of pressure variation in the diffuser 3at the point of communication with the pipe 11. With this arrangement, the plug 7 will move to different positions in response to variations in the relative pressures in the chamber 4- and the point of communication of the pipe 11 with the diffuser, and will therefore proportion the effective throat of the diffuser, in accordance with variations in the amount of fluid traversing the diffuser.

It will, of course. be understood that the pressure in the diffuser 3 will always be higher than the pressure in the inlet chamber 4 when the ejector is in operation. However, the pressure ratio, or in other words, the differential pressure acting on the piston 8, will vary as the density of the medium in the chamber 4 varies. When starting up the pressure in the diffuser will preponderate over the pressure in the inlet chamber to a much greater extent than when a partial vacuum is established in the chamber 4, consequently when the quantity of medium to be removed is large the plunger ,7 is raised, and when the quantity is small the plunger 7 is lowered It will be understood that the apparatus of Figure 1 is merely illustrative, and that under ordinary working conditlons, the difference in pressure existing in'the cylinder 9 above and below the piston 8 may not be sufficient to overcome friction and the inertia tion of the plug 7. It may therefore be desirable to connect the pipes 10 and 11 to the operating cylinder of a light and sensitive relay, which will control the delivery of operating medium to the cylinder 9 in re- ,sponce to "ariations in the pressure differances between the chamber 4 and the diffuser. It will also be apparent that under ordinary conditions it will be desirable to employ some means such for example as a dashpot, for preventing the slight fluctuations in pressure within the diffuser 3 from aflectin the operation of the plug 7 and that the dashpot may be operatively connected to either the relay or to the piston 8.

In Fig 3, I have shown a relay mechanism which may be employed, in controlling the piston 8 and hence the plug 7. trated, this mechanism comprises a cylinder 20 in which a piston 21 operates in response to variationsin pressure in the two pipes 10 and 11 which connect the ejector inlet 5 and the diffuser 3 with opposite ends of the cylinder 20. A pilot valve 22 is shown as adapted to be operated by the piston 21 and controls the delivery of a relatively high pressure actuating fluid to andufrom the cylinder 9 through the pipes 10 and 10". Actuating fluid, preferably oil, may be sup plied to the pilot valveby means of a pipe 23, and is carried ofi by means of exhaust pipes 24 and '25.- I have also 'shown a piston 26 connected to the piston 21 for preventing slight fluctuations in pressure from afiecting the operation of. the piston 21. The piston 26 loosely fits ina closed cylinder 27, or may be provided with a restricted hole or passageway so as to allow a limited flow o/f fluid past the piston so that it may move only under the influence of aforce of reasonable duration.

In Fig. 4, I have shown a dashpot as con nected directly tothe plug-controlling piston 8 in order to revent-movements in response to minor ami discontinuous fluctuations in the pressures. As shown,.the dashpot consists of a piston 28 having a restricted opening or by-pass 29 and adapted to slide in a cy inder 30. The cylinder 30 may be filled with oil or any other fluid.

In Figure 2, I have shown an embodiment of my invention in which a single nozzle 6',

for delivering im elling fluid through the chamber 4' is em oyed. The chamber 4 is also provided wit a port 5', which is adapted to communicate with a receptacle to be evacuated and means are employed for automatically varying the effective area of the throat or of the entire difluser tube.

The means illustrated consists of a conical 7 which extends axially of the difiuser plu , and is located in front of, and in alinement with, the nozzle 6'. The plug 7 is .provided with automatic means-for moving itin response to variations in the pressure existing in the chamber 4'. The means illustrated consists of a piston 8, which is located in a cylinder 9 and whichis rigidly secured to As illusconditions the piston 8 will move in response to variations between atmospheric pressure, as exerted on one side and chamber 4 pressure, as exerted on the other side. A spring 12, having the functions of the s rin 12 of F i ure 1, is also employed for P s g opposing the motion of the piston occasioned by a preponderance of the atmospheric pressure over that of the chamber 4'. In this apparatus, just as in-the apparatus illustrated in Figure 1, it may be desirable to employ a dashpot in connection with the piston 8', and it may also be desirable to operate the plug 7 through the agency of a relay valve which itself operates in response to variations in pressure within the chamber 4'.

In Fig. 5, I have shown a relay mechanism which may be employed for magnifying the force exerted by the pressure of the fluidin the ejector inlet 5. As shown, the pipe 10' is connected to one end of a cylinder 31, in

. which a piston 32 operates. A spring 33 in the other end of the cylinder 31 is adapted to oppose the force of the fluid pressure. The piston 32 actuates a pilot valve) 34, which controls the delivery of relatively high pressure actuatin fluid to and from the plug controlling'cylin er 9'. As illustrated. high pressure fluid, such as oil, may be delivered tothe pilot valve 34, by means of a pipe 35, and a pipe 36 is adapted to carry away the fluid exhausted from the cylinder 9'. I have also shown a dashpot 37 connected to the pilot valve 34' for preventing a response to discontinuous and minor pressure fluctuaa holclosed cylinder 40 and is provided with a restricted passageway or bypass 41 for allowing the passage of fluid from one, side of the piston 39 to the other under the influence of a reasonable continuous and powerful force.

In the apparatus illustrated in Figure 2, I have provided means for delivering a coolof a water jacket 14 surroundin the diffuser, including the convergent, divergent and throat portions thereof and means for introducing cooling water' into the interior of the plug 7 The water jacket 14 preferably receives cooling water through a pipe or passage 15 and discharges it through a passage 16. Cooling water is preferably de-.

livered to the apex of the conical plug 7 through a pipe 17, which extends axially of mg medium to the difiuser 3', whichconsists' traverses the diffuser. By so doing, the

volume per unit of weight of the propelling fluid is materially reduced, and therefore the work which it must do to discharge itself against the outlet pressure is reduced, thereby rendering a. greater amount of ener y available for expelling the medium from t e chamber 4. A propelling medium with a lower initial velocity or containing less ki-- netic energy per unit of weight at the nozzle outlet, is therefore capable of discharging a larger volume or weight of medium from the chamber 4 to the outlet of the diffuser than if it were not condensed or cooled.

Although it is not possible to condense all the motive fluid or steam used as the propelling medium while it is in motion, if this were possible, it will be readily seen that the resulting water of condensation would be moving with the velocity of steam discharged from the outlet of the nozzle 6. The pressure against which this moving jet of water could discharge itself would be many thousand times the pressure against which steam moil ifng at the same velocity could discharge itse In the apparatus of Figure 2 the plug 7' is not only adapted to vary the effective area of the ejector 3', but itmay also be so proportioned that 1t will enter the discharge end of the nozzle 6 and therefore cut down the delivery of steam by that nozzle to the ejector. It will be apparent that as the absolute pressure in the chamber 4 decreases, the plug 7 will move further into the diffuser, since a smaller volume of fluid is being discharged through the diffuser, and that at a determined pressure within the chamber 4, the amount of fluid entrained in the chamber 4 will be so reduced that the volume of steam issuing from the nozzle 6' may also be reduced. At this pressure the apex of the plug 7 will enter the nozzle 6 and will start to reduce the discharge of steam from the nozzle.

In my copending application for fluid translating devices, Serial No. 861,630, filed September 14, 1914, I have disclosed and claimed an ejector in which means are provided for varying the effective area of a nozzle of the ejector in accordance with variations in the amount of fluid to be ejected, and in which means are provided for varying the expansion ratio of the nozzle. The ejector described and illustrated is provided with a needle valve which extends through the steam inlet chamber into the throat of the nozzle and is controlled by a piston subjected on one side to the pressure of the fluid entering the ejector, and on the other side to the pressure of the fluids passing through the diffuser. Variations in the differential pressure acting on the piston cause the needle valve to move intoor out of the nozzle, thereby changing the effective area and expansion ratio of the nozzle.

In my copending application for fluid translating devices, Serial No. 861,634, filed September 1471914, I have disclosed and claimed an ejector which is provided with means responsive to variations in the amount of fluid to be ejected for controlling direct communication between the diffuser and the inlet passage of the ejector. The ejector described and illustrated is of the two stage type and has a bypass from inlet passage of the ejector to the throat of the second stage diffuser. This bypass is provided for the reason that the first stage of the ejector is designed to handle only a relatively small amount of fluid, consequently when the quan tity of fluid becomes relatively large a part of it is bypassed around the first stage of the ejector to the throat of the second stage.

In my copending application Serial No. 861,633, filed September 14, 1914, I have illustrated, described and claimed a single stage ejecting device communicating with a source of medium to be expelled, and a nozzle for delivering expelling or motive fluid through the diffuser. The nozzle is capable of movement toward and away from the inlet end of the diffuser and this movement is controlled by pressure variations within the ejecting device. Means are also disclosed and claimed for varying the effective throat of the movable nozzle in response to variations in the pressure encountered ,-within the apparatus.

It will be apparent that my invention may be employed in connection with ejectors employing a liquid, a condensable or a noncondensable fluid as the propelling medium, and that it may be employed in connection with ejectors adapted to convey or eject a liquid or non-condensable fluid. For these reasons I have employed the term fluid in its broadest sense throughout the entire application, since I do not wish to limit the invention to apparatus employing either compressible or non-compressible fluids as the impelling or the impelled medium.

It will also be apparent that while I have illustrated but two modifications of my invention, various changes, modifications, substitutions, omissions and additions may be made without departing from the spirit and scope of the invention as set forth by the appended claims.

What I claim is:

1. An air and non-condensable fluid ejector for a steam-power plant condenser ejector for a steam-power plant condenser j wherein a low absolute or highly vacuous pressure normally obtains comprising a chamber adapted for communications with apparatusof the character designated, a dif- -fuser communicating with the chamber, an expanding nozzleof the divergent type for transforming steam at high pressure into able fluids undergoing velocity-pressure con version in the diffuser, and means cooperating with the diffuser, including the converging portion thereof, for. condensing a part of the steam of the mixture in' order to improve the performance of the ejector.

2. An air and non-condensable fluid wherein a low absolute or highly vacuous pressure normally obtains comprising a chamber adapted for communication with apparatus of the character designated, a diffuser communicatingswith the chamber, an

expanding nozzle, of the -a yp o transforming, steam at;

gh pressure a into densation of 'a part of the steam of the mixture throughout the length of the diffuser in order to improve the performance of the ejector. I

4. The method of removing fluid medium from a region of low absolute or highly vacuous pressure, which consists in subjecting the medium to be removed to the entraining action of a stream of expansible and condensable fluid moving at a high velocity secured by expansion from a relatively high to a relatively low absolute or highly vacuous pressure, in converting the velocity energy of said fluid and the entrained medium into potential energy in the form of pressure, and. in cooling a portion of the stream of expansible and condensable fluid during the period of velocity-pressure conversion in order that the velocity energy 'may be more effectively utilized in raising the pressure of the non-condensed portion of said fluid and the entrained medium.

5. The method of removing fluid medium from a region of low absolute or highly vacuous pressure, which consistsjin subjecting the medium to be removed to the entraining action of a stream of expansible and condensable fluid moving f at a high velocity secured by expansion from a relatively high to a relatively low absolute or steam having low."absolutelor ihighly ,v acuous pressure and moving at high velocity for discharging the high-velocity steam'in a jet across at least a portion of the space of said chamber and into said difluser, .the high velocity jet entraining air and non-condensable fluids from said chamber and the mixture of steam, air and non-condensable fluids undergoing velocity-pressure conversion in diffuser, including converging, diverging and throat portions thereof, in order to condense a portion of the steam of the mixture to improve the performance of the ejector.

3. An air and non-condensable fluid ejector for a steam-power plant condenser wherein a low absolute or highly vacuous pressure normally obtains comprising a chamber adapted for communication with apparatus of the character designated, a diffuser communicating with the chamber, an expanding nozzle of the divergent type for transforming steam at high pressure into steam having low absolute or highly vacuous pressure and movin at high velocity and for discharging the igh-velocity steam highly vacuous pressure, in converting the velocity energy of said fluid and the entrained medium into potential'energy in the form of pressure, and in condensing at least a part of the outer marginal portions of said expansible and condensable fluid dur-v ing the period of velocity-pressure conversion in order that the velocity energy may be more effectively utilized in raising the pressure-of the non-condensed portion of said fluid and the entrained medium.

6. The method of removing fluid medium from a region of low absolute or highly vacuous pressure. and discharging it into a region of higher pressure in order to maintain the region at a low absolute or highly in a jet across at least a portion of the space erating with the difluser for effecting convacuous pressure, which consistsin sub ecting the medium to be removed to the entraining action of a jet of steam moving at hi h velocity secured by expansion from a re a-v tively high to a relatively low absolute or highly vacuous pressure, in converting the kinetic energy of the steam and entrained medium into potential energy in the form of pressure, and in causing a volumetric'contraction of the moving stream of medium and steam by condensing at least a portion of the steam while the kinetic energy is being changed into potential energy in addition to that normal y occasioned by the invelocity-pressure conversion, whereby the kinetic energy may be more effectively uti1-- ized for increasing the pressure. I

7. In combination in an ejector, a comcreasing pressure during the period 7 of a structure followed by a diverginv bining and diffuser tube, means for delivering motive fluid at high velocit thereto, external means for cooling the uids passing through the tube, movable means for varying the effective area of the tube, and means for cooling said last-mentioned means.

8. Ejector apparatus for raisingthe pressure of elastic fluid from a pressure below atmospheric pressure to a higher pressure comprising the combination with divergent nozzle structure whose outlet area is materially greater than its throat area for expanding elastic motive fluid into a high velocity jet, of means for conducting elastic fluid to be compressed to contact with the motive fluid jet while the fluid to be compressed is at a pressure below atmospheric pressure, a difluser in which the mixture of fluids decreases in velocity and increases in pressure, said diffuser having a throat, and means for extracting heat from the walls of said diffuser at said throat.

9. A single stage ejector for increasing the pressure of elastic fluid from a pressure below atmospheric pressure to a higher pres sure comprising divergent nozzle structure whose outlet area is materially greater than its throat area for expanding elastic motive fluid into a high velocity jet, a chamber in which said jet entrains the elastic fluid to be compressed while at a pressure below atmospheric pressure, a diffuser having a converging section adjacent said nozzle section, and a cooling jacket external to sa'fl diffuser for extracting heat from the mixture of mo tive and entrained fluids while in said converging and diverging sections.

10. The method of raising the pressure of elastic fluid, which consists in expanding elastic motive fluid into jet formation, entraining elastic fluid to be compressed, decreasing the velocity and increasing the pressure of the mixture of motive and entrained fluids while traversing a convergent tubular passage, and extracting heat from the mixture through the inner and outer walls of the passage.

11. Ejector apparatus comprising a suction chamber, nozzle structure, diffuser structure communicating with said suction chamber, and a cooling jacket closed at its and adjacent said suction chamber disposed in said diffuser and spaced therefrom to form a passage for the mixture of motive and entrained fluids;

12. Ejector apparatus comprising nozzle structure, a tubular diffuser havin a convergent wall at its end adjacent said nozzle structure, and a cooling jacket disposed within said diffuser and spaced therefrom to form a passage for the mixture of motive and entrained fluids, said cooling jacket adjacent said nozzle structure decreasing in external diameter to form with the iconvergent end of said diffuser a convergent tubular passage.

13. Ejector apparatus comprising nozzle structure, a tubular diffuser, anda cooling jacket extending substantially throughout the entire length of said diffuser within the same and spaced therefrom to form a convergent diffuser passage.

14. Ejector apparatus comprising nozzle structure, a'tubular diffuser, and a cooling jacket extending substantially throughout the entire length of said diffuser within the same and spaced therefrom to form a convergent-divergent diffuser passage.

15. Ejector apparatus comprising a suction chamber, nozzle structure, a tubular diffuser, anda cooling jacket disposed within said diffuser and terminating within said suction chamber, said jacket spaced from said diffuser to form a passage for the mixture of motive and entraining fluids.

16. Ejector apparatus comprising a suction chamber, nozzle structure, diffuser structure communicating with said suction chamber, a cooling jacket closed at its end adjacent said suction chamber disposed in said diffuser and spaced therefrom to form a passage for the mixture of motive and entrained fluids, and a cooling jacket surrounding said diffuser.

17. Ejector apparatus comprising ndzzle structure, a tubular diffuser having a convergent wall at its end adjacent said nozzle structure, a cooling jacket dis osed within said diffuser and spaced theref f'om to form a passage for the mixture of motive and entrained fluids, said cooling jacket adjacent said nozzle structure decreasing in external diameter to form with the convergent end of said diffuser a convergent tubular passage, and a cooling jacket surrounding saiddiffuser.

18. Ejector apparatus comprising nozzle structure, a tubular diffuser, a cooling jacket extending substantially throughout the entire length of said diffuser within the same and spaced therefrom to form a convergent diffuser passage, and a cooling jacket surrounding said diffuser.

19. Ejector apparatus comprising nozzle structure, a tubular diffuser, a cooling jacket extending substantially throughout the entire length of said diffuser within the same and spaced therefrom to form a convergentdivergent diffuser passage, and a cooling jacket surrounding said dlffuser.

20. Ejector apparatus comprising a suction chamber, nozzle structure, a tubular diffuser, a cooling jacket disposed within said diffuser and terminatingwithin said suction chamber, said jacket spaced from said diffuser to form a passage for the mixture of motive and entrained fluids, and a coolingjacket surrounding said diffuser.

'21. Ejector apparatus comprising nozzle structure cooperating diffuser structure, a member disposed within said diffuser structure and spaced therefrom to form a convergent passage for the mixture of motive and entrained fluids, and means surrounding said diffuser for extracting heat from said mixture.

22. Ejector apparatus comprising nozzle structure, cooperating difluser structure, a member disposed within said diffuser structure and spaced therefrom to form a convergent-divergent passage for the mixture of motive and entrained fluids, and means surrounding said difi'user for extracting heat from said mixture.

23. The method of raising the pressure of elastic fluid, which consists in expanding elastic motivefluid' into jet formation, entraining elastic fluid to be compressed, decreasing the velocity and increasing the pressure of the mixture of motive and entrained fluids while traversing a convergent tubular passage, and extracting heat from the mixture through the inner wall of the passage.

24. An ejector comprising diffuser structure having a convergent portion, nozzle structure delivering into said diffuserstructure elastic motive fluid in which is entrained said convergent portion of said diffuser structure, said means comprising fluid conducting structure within said diffuser structure and spaced therefrom to form a passage for said mixture.

25. Ejector apparatus comprising a suction chamber, nozzle structure, diffuser structure communicating with said suction chamber, and structure for absorbing heat from the motive fluid and fluid to be compressed disposed in said suction chamber and within said diffuser. 26. Ejector apparatus comprising a suction chamber, nozzlestructure, diffuser structure communicating with said suction chamber, and structurefor absorbing heat from the motive fluid and fluid to be compressed disposed in said suction chamber and within said diffuser and spaced from the latter to form a passage for the mixture of motive fluid and the fluid entrained thereby.

In testimony whereof, I have hereunto subscribed my name this 21st day of August,

. HENRY F. SCHMIDT. 

